This invention relates to a method of compacting high temperature metal powders and, more particularly, to a method of producing complex configuration parts from high temperature metal powders by compacting a heated mold containing the powder in the axial direction while restricting the mold in the lateral direction, such as can be accomplished between the dies of a conventional forging press in conjunction with a compaction cylinder.
High temperature metallurgy has advanced rapidly in recent years to meet ever increasing demands. The most significant advances in the area of high temperature alloys appear to be in the aircraft and aerospace industries. High temperature metals, such as titanium or superalloys of the nickel-base, cobalt-base or iron-base variety, are primarily used in such environments wherein operating temperatures range from about 1200.degree. to 1800.degree. F. and stresses are high. Powder metallurgy techniques are typically employed in producing components or structure from these alloys. Such components are particularly suited for critical jet engine applications, such as discs, shafts, turbine blades, nozzle vanes, seals, and other propulsion system uses in which high temperatures and stresses are encountered.
Current methods of compacting high temperature metal powders to complex shapes include hot isostatic compacting, such as that disclosed in Chandhok, U.S. Pat. No. 3,700,435 and Havel U.S. Pat. No. 3,622,313. Hot isostatic compacting typically involves transmitting pressure through a fluid medium to a deformable container holding the powder. The medium transmits a uniform pressure throughout the chamber holding the liquid or gaseous medium and the container. When an inert gas, such as argon, is used as the pressure medium in an isostatic press, large amounts of energy are required for heating and for compressing. In an isostatic press, the same unit pressure, of about 15 ksi, is applied against all areas of the deformable container for an excessive period of time, such as four to eight hours, resulting in a uniform density throughout the compacted article. Isostatic compacting in an autoclave is used primarily in the forming of complicated or intricately shaped, fully dense articles, which heretofore were not able to be successfully formed between the dies in a forging press. One of the unexpected advantages of the method of the present invention is that an equivalent high temperature metal powder component may be quickly formed by relatively high pressure uniaxial compression of a particular heated mold holding the powder in a centrally located cavity. It was previously thought that the strength of a low thickness to diameter ratio components formed by relatively high pressure compression at high temperatures was inferior to that of a component formed by hot isostatic pressing.
Accordingly, an economical and effective method is desired for producing complex configuration parts from high temperature metal powder.